AS Jun 12.pdf

Do not write
outside the
box

2
Section A
Answer all questions in the spaces provided.
85Rb

87Rb

1

The element rubidium exists as the isotopes

1 (a)

State the number of protons and the number of neutrons in an atom of the
isotope 85Rb

and

Number of protons .............................................................................................................
Number of neutrons ...........................................................................................................
(2 marks)
1 (b) (i)

Explain how the gaseous atoms of rubidium are ionised in a mass spectrometer.
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(2 marks)

1 (b) (ii) Write an equation, including state symbols, to show the process that occurs when the
first ionisation energy of rubidium is measured.

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(1 mark)
1 (c)

The table shows the first ionisation energies of rubidium and some other elements in
the same group.
Element
First ionisation
energy / kJ mol–1

sodium

potassium

rubidium

494

418

402

State one reason why the first ionisation energy of rubidium is lower than the first
ionisation energy of sodium.
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(1 mark)

(02)

WMP/Jun12/CHEM1